Question

A combinational circuit that performs the addition of two input bits and a carry from the previous lower significant position is called

Answer 1

full adder is the required circuit...

Hope it helped

Answer 2

One that performs addition of  3 bits – 2 significant bit and a previous carry is called a full adder. The name of the former comes from that fact that the 2 half adders are needed to implement a full adder.  

The truth table is:

 

x              y              z              C             S

 

0              0              0              0              0

0              0              1              0              1

0              1              0              0              1

0              1              1              1              0

1              0              0              0              1

1              0              1              1              0

1              1              0              1              0

1              1              1              1              1